It is a trend that light emitting diode (LED) is widely used to replace conventional light bulb in various occasions, such as LED projector light source, spot light, traffic signal light and automobile brake light. A light bulb made of LEDs has the advantage of small volume but is limited in luminosity, which limits its application. To increase its luminosity, light source made of a plurality of LEDs is necessary, causing a proportional increase in the operation current. However, the conventional LED light bulbs rely on metallic bracket for the LEDs to dissipate heat, which is not sufficient for an operation at high electric current, and therefore the luminosity is still limited. To operate the LED light bulbs at high current and therefore high luminosity for a long time is easy to burn out the LED chips therein. To tackle this disadvantage, a multi-layer structure wherein the LED chips are attached on a thin copper sheet that is mounted on a metallic block by a gluing material. Therefore, as heat is generated in the chips, it will be transferred quickly downward to the metallic block. However, the design is still not efficient enough, and therefore the durability of the LED chips is still limited.